1. Field of the Invention
The invention relates to a clamp for section tubes, and more particularly, to a clamp for production of readily assembled and dismantled framework structure made up with section tubes, in particular for use at fairs and exhibitions.
2. Description of Related Art
Modular panel frame assembly system is widely used in applications as office partitions, display racks, and window supports. A typical conventional expandable clamp for modular panel frame assembly often has opposing jaws that are always separated from each other by a substantial space. The frame members have at least one longitudinal central slit which is able to be engaged by the expandable clamp. Some former jaws are rigid which are not able to be bent. However, clamp having such kind of jaws has a main drawback that the jaws is fixed and not able to be longitudinally adjusted. Such clamp can only be used with predetermined modular panel and the assembly of the frame may become loose after use.
Shown in FIGS. 10 and 11 is an improved clamping means 9 for inter connecting more than one profile tubes (not shown) together to set up a framework structure for use at fairs and exhibitions. The profile tubes 8 has at least four identical side surfaces 81, each having a longitudinal slit 82 defined therein. The clamping means 9 has a shell 90 and at least one latch 92. The shell 90 has at least one longitudinal chamber 91 which is able to slidably receive the latch 92. The latch 92 has a cover containing a hooked lever 93 which is able to be pulled by a screw 94. The screw 94 is able to be buttoned down. In assembly, a user is able to press down the screw 94 and then insert the latch 92 into the chamber 91. When the screw 94 passes a through hole 95 defined in the shell 90, it upsprings and is matchingly received in the hole 95, thus making the latch 92 stably fixed with respect to the shell 90. The shell 90 may have a pair of opposite side guiding grooves 96 matching a pair of opposite guiding bars 83. When the shell 90 is inserted into the profile tube 8 as particularly shown in FIG. 11, it is able to be fixed there with several screws 84. A screw lever 85 can be used to access the screw 94 via an opening 86 defined in the side surfaces 81. The screw 94 can be tightened or loosened to control the hooked lever 93 to lock or release another profile tube 8 (not shown). In order to facilitate the access of the screw lever 85, an usher tube 97 has to be provided mounting between a pair of parallel rails 98.
Such kind of clamping means 9 has an adjustable hooked lever 93 which is able to be pulled back into the shell 90. It is able to be applied to profile tubes having various thickness. But such kind clamping means has some shortcomings. First, the hooked lever must be flexible. If it is rigid, it will not be able to be pulled into the shell and cannot lock the profiled tube. But a flexible hooked lever will significantly decrease a strength of the hooked lever. Such clamp cannot be applied to heavy duty assemblies of huge profile tubes. Second, an adjustable distance of the hooked lever is decided by an eccentric rate of an eccentric wheel controlling the hooked lever. The eccentric rate is usually small, which means the adjustable distance of the hooked lever is usually small.